1. Field of the Invention
This invention generally relates to rotary drive tools such as screwdrivers and wrenches and, more particularly, to reversible, ratchetless tools whose turning speed is selectable by a user.
2. Description of Related Art
Reversible, ratchet tools utilizing conventional pawl, ratchet and spring assemblies are generally satisfactory, except that such tools tend to be noisy during operation due to the generation of a characteristic "clicking" sound. Also, such tools are subject to backlash which requires them to be turned through a small, but non-negligible, distance before the tool drivingly re-engages a fastener. Moreover, such tools are sensitive to dust, grime and other contaminants, thereby subjecting them to increased wear. Reversible, ratchet tools of this type are exemplified by U.S. Pat. Nos. 1,904,621; 2,003,155; 2,897,932; 3,621,739; 3,679,031; 3,908,487; 4,362,073; and 4,485,699.
It is also known to increase the turning speed of such tools by pushing axially along a drive shaft against a fastener to be turned. Experience has shown, however, that such tools are awkward to operate, particularly when the fastener is about to be threaded into a threaded hole. At such time, it is desirable to use the higher turning speed. However, since this requires the user to push hard against the fastener, often the fastener is pushed over, thereby requiring the user to re-position the screw in the hole--a laborious and aggravating process.